Electronic circuits using small signal transistors and integrated circuits are easily damaged by high voltage transients that may appear on the line due to lightning, switching transients, or power line induction. Accordingly, some form of transient and over voltage protection must be used to protect the solid state circuits, for example, in the electronic telephone sets (telephone station) and related equipment.
Since technology used for making integrated circuits cannot provide high enough breakdown voltage, other devices are employed. For example, one or more external zener diodes are placed across the line to provide over voltage protection. When the input voltage exceeds the zener (breakdown) voltage, the zener conducts and holds the voltage input to the electronic circuit at the rated zener voltage.
Another type of protector circuit is disclosed in the copending application of Shannon et al entitled Compact Solid State Protector Device, Ser. No. 082,625, filed Aug. 7, 1987. Briefly, as described therein, the protector circuit comprises two bidirectional solid state voltage sensitive switch devices with an associated ground terminal, two variable resistance devices, and line protector means for protecting the solid state protector device from high voltage transients and abnormal currents. The disclosed protector circuit provides protection of electronic equipment from voltage surges by electronically switching the voltage surge from line to ground. Additionally, the protector circuit protects the electronic equipment and itself from high current surges on the line by increasing the impedance of the line thereby reducing the current to the equipment to the desired value. Upon cessation of the high voltage or current surge, the activated protector device returns to the inactive or idle state, allowing the line circuit to function in the usual manner.
While such protector circuits provide improvement in the areas intended, there is still a great need to provide a compact enclosure in which the protector circuit can be mounted and which provides for safety requirements and minimizes space while accepting standard line connectors and providing standard mounting plug-in connectors.
Accordingly, a principal object of the present invention is to provide a solid state protector device for use as a consumer circuit protector for solid state telephone and related equipment.
Another object of the present invention is to provide a solid state protector device which is constructed and arranged to be mounted in standard jacks and to receive standard connectors at the customer's premises.